This book provides an accessible and self-contained introduction to the theory of algebraic curves over a finite field, a subject that has been of fundamental importance to mathematics for many years ...and that has essential applications in areas such as finite geometry, number theory, error-correcting codes, and cryptology. Unlike other books, this one emphasizes the algebraic geometry rather than the function field approach to algebraic curves.
The authors begin by developing the general theory of curves over any field, highlighting peculiarities occurring for positive characteristic and requiring of the reader only basic knowledge of algebra and geometry. The special properties that a curve over a finite field can have are then discussed. The geometrical theory of linear series is used to find estimates for the number of rational points on a curve, following the theory of Stöhr and Voloch. The approach of Hasse and Weil via zeta functions is explained, and then attention turns to more advanced results: a state-of-the-art introduction to maximal curves over finite fields is provided; a comprehensive account is given of the automorphism group of a curve; and some applications to coding theory and finite geometry are described. The book includes many examples and exercises. It is an indispensable resource for researchers and the ideal textbook for graduate students.
We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated ...creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be modeled by elastic interfaces moving on disordered energy landscapes.
Hypersensitivity reactions to betalactams (BLs) are classified as immediate or nonimmediate. The former usually appear within 1 h of drug-intake and are mediated by specific IgE-antibodies. ...Nonimmediate reactions are those occurring more than 1 h after drug-intake, and they can be T-cell mediated. The diagnostic evaluation of allergic reactions to BLs has changed over the last 5 years, for several reasons. Major and minor determinants are no longer commercially available for skin testing in many countries. In immediate allergic reactions, the sensitivity of skin testing and immunoassays is decreasing and new in vitro methods, such as the basophil activation test, are gaining importance for diagnosis. For nonimmediate reactions, skin testing appears to be less sensitive than previous results, although more studies need to be carried out in this direction. Nevertheless, the drug provocation test is still necessary for diagnosis.
The 6-min walk distance (6MWD) predicted values have been derived from small cohorts mostly from single countries. The aim of the present study was to investigate differences between countries and ...identify new reference values to improve 6MWD interpretation. We studied 444 subjects (238 males) from seven countries (10 centres) ranging 40-80 yrs of age. We measured 6MWD, height, weight, spirometry, heart rate (HR), maximum HR (HR(max)) during the 6-min walk test/the predicted maximum HR (HR(max) % pred), Borg dyspnoea score and oxygen saturation. The mean ± sd 6MWD was 571 ± 90 m (range 380-782 m). Males walked 30 m more than females (p < 0.001). A multiple regression model for the 6MWD included age, sex, height, weight and HR(max) % pred (adjusted r² = 0.38; p < 0.001), but there was variability across centres (adjusted r² = 0.09-0.73) and its routine use is not recommended. Age had a great impact in 6MWD independent of the centres, declining significantly in the older population (p < 0.001). Age-specific reference standards of 6MWD were constructed for male and female adults. In healthy subjects, there were geographic variations in 6MWD and caution must be taken when using existing predictive equations. The present study provides new 6MWD standard curves that could be useful in the care of adult patients with chronic diseases.
Muscle strength plays an important role in determining risk for falls, which result in fractures and other injuries. While bone loss has long been recognized as an inevitable consequence of aging, ...sarcopenia—the gradual loss of skeletal muscle mass and strength that occurs with advancing age—has recently received increased attention. A review of the literature was undertaken to identify nutritional factors that contribute to loss of muscle mass. The role of protein, acid–base balance, vitamin D/calcium, and other minor nutrients like B vitamins was reviewed. Muscle wasting is a multifactorial process involving intrinsic and extrinsic alterations. A loss of fast twitch fibers, glycation of proteins, and insulin resistance may play an important role in the loss of muscle strength and development of sarcopenia. Protein intake plays an integral part in muscle health and an intake of 1.0–1.2 g/kg of body weight per day is probably optimal for older adults. There is a moderate inverse relationship between vitamin D status and muscle strength. Chronic ingestion of acid-producing diets appears to have a negative impact on muscle performance, and decreases in vitamin B
12
and folic acid intake may also impair muscle function through their action on homocysteine. An adequate nutritional intake and an optimal dietary acid–base balance are important elements of any strategy to preserve muscle mass and strength during aging.
We experimentally investigate the process of intramolecular quantum interference in high-order harmonic generation in impulsively aligned CO2 molecules. The recombination interference effect is ...clearly seen through the order dependence of the harmonic yield in an aligned sample. The experimental results can be well modeled assuming that the effective de Broglie wavelength of the returning electron wave is not significantly altered by the Coulomb field of the molecular ion. We demonstrate that such interference effects can be effectively controlled by changing the ellipticity of the driving laser field.
NASA’s InSight mission to Mars will measure seismic signals to determine the planet’s interior structure. These highly sensitive seismometers are susceptible to corruption of their measurements by ...environmental changes. Magnetic fields, atmosphere pressure changes, and local winds can all induce apparent changes in the seismic records that are not due to propagating ground motions. Thus, InSight carries a set of sensors called the Auxiliary Payload Sensor Suite (APSS) which includes a magnetometer, an atmospheric pressure sensor, and a pair of wind and air temperature sensors. In the case of the magnetometer, knowledge of the amplitude of the fluctuating magnetic field at the InSight lander will allow the separation of seismic signals from potentially interfering magnetic signals of either natural or spacecraft origin. To acquire such data, a triaxial fluxgate magnetometer was installed on the deck of the lander to obtain magnetic records at the same cadence as the seismometer. Similarly, a highly sensitive pressure sensor is carried by InSight to enable the removal of local ground-surface tilts due to advecting pressure perturbations. Finally, the local winds (speed and direction) and air temperature are estimated using a hot-film wind sensor with heritage from REMS on the Curiosity rover. When winds are too high, seismic signals can be ignored or discounted. Herein we describe the APSS sensor suite, the test programs for its components, and the possible additional science investigations it enables.
Abstract
The emerging CdTe–BeTe semiconductor alloy that exhibits a dramatic mismatch in bond covalency and bond stiffness clarifying its vibrational-mechanical properties is used as a benchmark to ...test the limits of the percolation model (PM) worked out to explain the complex Raman spectra of the related but less contrasted Zn
1−x
Be
x
-chalcogenides. The test is done by way of experiment (
$$x\le 0.11$$
x
≤
0.11
), combining Raman scattering with X-ray diffraction at high pressure, and ab initio calculations (
$$x$$
x
~ 0–0.5;
$$x$$
x
~1). The (macroscopic) bulk modulus
$${B}_{0}$$
B
0
drops below the CdTe value on minor Be incorporation, at variance with a linear
$${B}_{0}$$
B
0
versus
$$x$$
x
increase predicted ab initio, thus hinting at large anharmonic effects in the real crystal. Yet, no anomaly occurs at the (microscopic) bond scale as the regular bimodal PM-type Raman signal predicted ab initio for Be–Te in minority (
$$x$$
x
~0, 0.5) is barely detected experimentally. At large Be content (
$$x$$
x
~1), the same bimodal signal relaxes all the way down to inversion, an unprecedented case. However, specific pressure dependencies of the regular (
$$x$$
x
~0, 0.5) and inverted (
$$x$$
x
~1) Be–Te Raman doublets are in line with the predictions of the PM. Hence, the PM applies as such to Cd
1−x
Be
x
Te without further refinement, albeit in a “relaxed” form. This enhances the model’s validity as a generic descriptor of phonons in alloys.
Summary This review describes the vitamin D status in different regions of the world with the objective of understanding the scope of hypovitaminosis D and the factors related to its prevalence that ...may contribute to the pathogenesis of osteoporosis and fragility fractures. Introduction Vitamin D status has been linked to the pathogenesis of hip fractures as well as other skeletal and non-skeletal disorders. The purpose of this review is to provide a global perspective of vitamin D status across different regions of the world and to identify the common and significant determinants of hypovitaminosis D. Methods Six regions of the world were reviewed—Asia, Europe, Middle East and Africa, Latin America, North America, and Oceania—through a survey of published literature. Results The definition of vitamin D insufficiency and deficiency, as well as assay methodology for 25-hydroxyvitamin D or 25(OH)D, vary between studies. However, serum 25(OH)D levels below 75 nmol/L are prevalent in every region studied whilst levels below 25 nmol/L are most common in regions such as South Asia and the Middle East. Older age, female sex, higher latitude, winter season, darker skin pigmentation, less sunlight exposure, dietary habits, and absence of vitamin D fortification are the main factors that are significantly associated with lower 25(OH)D levels. Conclusion Reports from across the world indicate that hypovitaminosis D is widespread and is re-emerging as a major health problem globally.
We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band ...light curves of SN 2007on and SN 2011iv are characterised by Δm15 (B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B- and H-band magnitudes differ by ~ 0.60 mag and ~0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that differ by ~ 14% and ~ 9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B − V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, 56Ni production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity–width relation, while the central density is an important second-order parameter. Within this context, the differences in the B − V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on.
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